Has anyone else had this problem??

When running the a/c - it will suddenly go to hot for no reason. I switch the temp control back and forth and it will got back to cool but I cannot adjust the temp w/o it going to hot again...so either I'm freezing or no a/c at all.

Any suggestions?? I just don't want to spend a ton of $$ taking it to a dealership if this is something minor.

Pull your middle temp control knob straight out. Look for a nut where the knob was. tighten that nut. I've got the same year highlander and it would happen whenever I turned a hard right until today, when it only blew hot air no matter what. Searched around and found out it happens to a lot of people and that its just the nut behind the knob (as opposed to the nut behind the wheel) :). Fixed in two minutes for me.

I had same problem w/my '04 Highlander. Temp control would often cut out after hitting a bump. Same as you, when I turned it down, then up again, it was OK for a while. I had it into the dealer for some other work last winter and had them take a look at it. They said it was just a loose connection to the temp control; they fixed it and it's been OK since. Maybe it was the same loose nut referred to by "austin99". Hope this helps!